Prolonged storage-induced changes in haematology parameters referred for testing

Referral of samples for the work-up of haematological disorders from remote laboratories can result in a delay in analysis.

The stability of the full blood count (FBC), differential count (DIFF), reticulocyte and peripheral blood smear (PBS) morphology during extended storage was evaluated.

Forty blood samples stored in ethylenediaminetetraacetic acid (EDTA) were analysed on an ADVIA® 120 haematology analyser. The samples (25% abnormal; 75% normal) were stored at room temperature (RT) and at 4 °C - 8 °C. Analysis of samples stored at RT was performed every 12 hours for two days. Analysis of samples stored at 4 °C - 8 °C was performed at 12 hours and subsequently every 24 hours for seven days.

FBC parameters (red cell count, haemoglobin) and DIFF parameters (percentages of basophils, lymphocytes and monocytes) were stable for at least 48 hours when stored at RT. Platelets were only stable for 12 hours and the white cell count was stable for 36 hours when stored at RT. Storing samples at 4 °C - 8 °C significantly increased the stability of most parameters, in particular, mean cell volume and percentage of reticulocytes. However, DIFF parameters were associated with lower stability at 4 °C - 8 °C. PBS morphology was compromised prior to 12 hours whether stored at RT or at 4 °C - 8 °C.

This study provides evidence that blood samples stored in EDTA at 4 °C - 8 °C for seven days are suitable for testing on the ADVIA® 120 analyser for the FBC and percentage of reticulocyte parameters. However, storage at 4 °C - 8 °C is not a solution for samples referred for DIFF and PBS morphology review.